JP2970881B2 - Flash light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash light emitting device, and more particularly, to detection of a voltage charged to a main capacitor in a flash light emitting circuit of a flash light emitting device used for photographing or the like.

[0002]

2. Description of the Related Art As is well known, the charging of a main capacitor in a flash light emitting device, that is, a strobe device is performed in such a manner that the output voltage of a step-up transformer is higher than the actually used voltage in order to shorten the charging time. Many have decided.
This aims at shortening the charging time by using a place where the rise of the charging curve of the main capacitor is sharp. That is, the charging mosquito Figure 7 - as shown in Bed, charging mosquitoes when using transformer high output voltage - the blanking a, but charging time T to reach the working voltage becomes shorter as T _1, the same as the operating voltage Charger when using output voltage transformer
Bed b, the charging time T to reach the working voltage becomes longer and T _2.

[0003] However, the use of such a high output voltage transformer has the advantage of shortening the charging time. In this case, if the charging voltage is not controlled, the charging voltage rises with time. Main capacitor and Xe
The withstand voltage of the discharge tube will be exceeded. Therefore, when such a transformer is used, it is necessary to stop the charging operation at the working voltage, and therefore, it is necessary to detect the charging voltage of the main capacitor. Generally, in order to detect the charging voltage, a neon lamp or a zener is conventionally used.
A voltage detecting element such as a diode is used.

As shown in FIG. 8, a voltage detecting circuit using a neon lamp includes a resistor R ₁ , a neon lamp Ne, resistors R ₂ , R ₂ connected in parallel with a main capacitor C.
₃ and a transistor Q,
When the boosting control signal CHRG for starting charging becomes "L" level, the battery voltage is boosted by the power supply circuit, passes through the diode D, and the charged charge is charged to the main capacitor C. Then, when the voltage of the main capacitor C increases and the charged voltage reaches the lighting voltage of the neon lamp Ne, the lamp Ne is turned on to indicate that the charging is completed.
Further, since the lighting current flows, the transistor Q is turned on, and the signal is inverted by the inverter I to start charging.
The boost control signal CHRG to be turned to “H” level, and charging is stopped. In the voltage detection circuit configured as described above, the charging voltage can be controlled by selecting the lighting voltage of the neon lamp to a desired charging stop voltage.

Further, the conventional voltage detection circuit shown in FIG.
The neon lamp Ne is replaced with a Zener diode TD, and the other configuration is the same as that of FIG. Also in this case, the charging voltage of the main capacitor C increases, and when the voltage of the capacitor C reaches the Zener voltage of the Zener diode TD, the Zener diode is turned on.
The transistor TD conducts, a Zener current flows, the transistor Q is turned on, its signal is inverted by the inverter I, the charge start signal CHRG becomes "H" level, and charging is stopped.

Further, a voltage detecting circuit in which the voltage of the main capacitor is divided by a resistor without using a voltage detecting element and the voltage is detected by a voltage detecting circuit is also known from Japanese Patent Application Laid-Open No. 2-193131. As this circuit is shown in FIG. 10, dividing the charge voltage of the main capacitor C by the resistance R _4, R _5, comparator that value - data CP _1, C
Determined by P _2, is lower than the preset voltage Vref, the determining that the voltage of the main capacitor does not reach the working voltage, DC / DC converter - continued activation of motor CO, equal to the voltage set If this happens, the operation of the DC / DC converter CO is stopped to stop charging the main capacitor.

[0007]

By the way, in a camera with a built-in strobe, when the charging voltage to the main capacitor of the strobe is lower than the voltage at which the xenon lamp of the flash discharge tube can emit light, or when the charging is several steps lower than the proper exposure. When the voltage is lower than the voltage, means for locking the release of the shutter to prevent a failed photograph from causing a large underexposure is adopted.

However, in the above-mentioned conventional voltage detecting circuit using a voltage detecting element such as a neon lamp or a Zener diode, since there is only one voltage detection level, a charge stop voltage and a light emission permission voltage are determined. When the release is pressed, the charge stop voltage, that is, the light emission is not permitted unless the battery is fully charged, so that the release during the flash charging cannot be performed, and the continuous shooting is performed. In this case, there is a disadvantage that the continuous shooting time becomes long and a shutter chance is missed. In the conventional voltage detection circuit shown in FIG. 10, the charge stop voltage and the light emission permission voltage can be separately detected by making the setting voltages Vref of the comparators CP ₁ and CP ₂ different from each other. However, a separate circuit for determining the voltage is required, so that the mounting space is increased and the cost of the camera is increased.

An object of the present invention is to provide a flash light emitting device which eliminates the above-mentioned conventional drawbacks and can separately detect a charge stop voltage and a light emission permission voltage.

[0010]

In order to achieve the above object, a flash light emitting device according to the present invention has a power supply boosting circuit for receiving a boosting control signal and boosting a power supply voltage, and is charged with the boosted voltage of the power supply boosting circuit. A main capacitor connected in parallel with the main capacitor, a series circuit of a pass capacitor and a voltage detecting element, and a divider for applying a divided voltage of the charging voltage of the main capacitor to a connection point between the pass capacitor and the voltage detecting element. A voltage circuit for detecting a charging voltage of the main capacitor according to an output signal of the voltage detecting element at the time of a boosting operation according to the boosting control signal. A diode is connected between the connection point of the element and the voltage dividing circuit. Furthermore, flash light emission device of the present invention includes a power supply voltage booster circuit which boosts the power supply voltage by receiving a boost control signal, and a main capacitor which is charged by the boosted voltage by the power supply voltage booster, it is charged in the main capacitor
Charging voltage detecting means for detecting the voltage which
The voltage of the main capacitor detected by the
If the voltage is lower than the in-capacitor charge completion voltage,
A return pulse signal is output and the charging voltage detection means
The main capacitor voltage detected by
And a signal output unit that outputs a non-pulse signal when the voltage is equal to or higher than the charge completion voltage of the power supply, and a power supply booster circuit that receives the boosting start signal and boosts the power supply voltage;
A main capacitor charged by the boosted voltage of the power supply boosting circuit, voltage dividing means for dividing the voltage of the capacitor,
Changing means for changing a voltage dividing ratio of the voltage dividing means in response to the boosting start signal.

[0011]

The charge voltage of the main capacitor is detected according to the output signal of the voltage detecting element at the time of the boosting operation according to the boosting control signal.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a block diagram of the configuration of a flash light emitting device showing the concept of the present invention. When a boost control signal (hereinafter, referred to as a CHRG signal) is input from a CPU 33 to a power boost circuit 29, the circuit 29 operates. The boosted voltage is applied to the main capacitor 16 through a rectifying diode 23 and a backflow preventing diode 24 to charge the electric charge. When the voltage of the main capacitor 16 reaches a predetermined voltage, the CPU 33 is charged by a charging voltage detecting circuit 32 comprising a series circuit of a pass capacitor and a voltage detecting element and a voltage dividing circuit for obtaining a divided voltage of the charging voltage of the main capacitor. And the CPU 33 outputs the CHRG signal to the power supply booster circuit 29.
Stop applying the signal.

Next, when the release switch 34 is depressed, the CPU 33 outputs a short CHRG signal to the power supply boosting circuit 29. At that time, the charging voltage detecting circuit 32
It is checked whether or not the CHUP signal is output from the CPU, and if it is output, the release is permitted and the trigger circuit 35
Outputs a trigger signal (hereinafter referred to as TRG signal)
The light emitting discharge tube 27 is excited by the trigger electrode 27t to emit light. FIG. 2 is an electric circuit of a flash light emitting device according to the first embodiment of the present invention, wherein a power supply boosting circuit 29 for boosting the voltage of a power supply battery 36 includes resistors 1, 2, and 3;
Capacitors 11, 12 and transistors 17, 18, 1
9, the step-up transformer 28, and the rectifying diode 23
Are connected as shown, and the CHRG signal is input to the base of the transistor 17 from a CPU (not shown). And
The output end of the power supply boosting circuit 29 through the rectifying diode 23 is connected to the charging voltage detecting circuit 32, the main capacitor 16, a light emitting discharge tube 27 including a Xe discharge tube,
The trigger circuits 35 are respectively connected.

The trigger circuit 35 includes a transistor 2
0, a series circuit of resistors 7 and 8, a series circuit of a resistor 9 and a thyristor 22 for starting light emission, a trigger capacitor 14, and a trigger transformer 26 are connected as shown, and a TRG signal is applied to the transistor 20. Activated when done
A high-voltage pulse voltage is applied to the trigger electrode 27t. The light emitting discharge tube 27 has a diode.
25 is connected in series, and a resistor 1
0 and the capacitor 15 are connected as shown.

The charging voltage detecting circuit 32 comprises a voltage dividing circuit comprising a series circuit of resistors 5 and 6, a pass capacitor 13, a resistor 4, a neon lamp 30, and a transistor 21.
, And a ripple absorbing capacitor 31. The connection point between the resistors 5 and 6 is connected to the connection point between the capacitor 13 and the resistor 4. The resistors 5 and 6 are voltage-dividing resistors for dividing the voltage of the main capacitor 16, and their resistance values are set so that the divided voltage becomes equal to the lighting voltage of the neon tube. Neon lamp 30
Is turned on when a predetermined voltage is applied, and the lighting voltage is set to the strobe light emission permission voltage.
The pass capacitor 13 serves to pass the current flowing through the resistor 5.

The operation of the flash light emitting circuit of the above-described first embodiment will be described below. (1) Charging Stop Operation First, in this charging stop operation, the DC / DC converter, that is, the power supply boosting circuit 29 is activated by the CHRG signal from the CPU, and the main capacitor 16 is charged. The voltage of the main capacitor 16 is divided by the resistors 5 and 6 and is applied to the neon lamp 30. The main voltage of the capacitor 16 is increased, the divided voltage is set lower than the charging stop voltage V _1, and reaches the ignition voltage V ₂ of the neon lamp 30, the neon lamp 30 is lit, the transistor 21 is turned on ,
The CHUP signal becomes “L” level, and upon receiving the signal, the CPU turns off the CHRG signal. Figure 3 shows this situation.
It is shown in (A). That is, FIG. 3A shows a normal charging operation, and the charging voltage detecting circuit 3 shown in FIG.
2 shows the voltage curves at points A and B respectively.
The curve at point A with respect to the voltage curve at point B can be easily set by the ratio of the constants of resistors 5 and 6.

(2) Light-emission permission voltage detection operation This light-emission permission voltage detection operation is performed by setting the charge stop voltage to V ₁ ,
If the emission permission voltage (= neon lighting voltage) is V ₂ , the main capacitor voltage is V _MC , and the neon extinguishing voltage is V ₃ ,
Now, if the main capacitor voltage is V ₂ ≦ V _MC <V ₁
At this time, when the release is pressed, the CPU checks the voltage of the main capacitor 16 so that the power supply boosting circuit 2
9 is activated for several ms to several tens ms. Then, the voltage between the diodes 23 and 24 is substantially equal to the main capacitor voltage V _MC.
A voltage equal to At the moment when this voltage is generated, the current flows through the pass capacitor 13 without flowing through the resistor 5.
Therefore, at that moment, point A has a main capacitor voltage V _MC
Will be generated, and since V ₂ ≤V _MC ,
The neon lamp 30 lights up.

After the neon lamp is turned on, the pass capacitor 13
Is increased by the neon lighting current and the current flowing through the resistor 6. Assuming that this voltage is V _C , the voltage applied to the neon lamp 30 at this time is V _MC −V _C
The neon lamp 30 is turned off when (V _MC -V _C ) ≦ the neon turn-off voltage V ₃ .

Looking at the above movements collectively, V ₂ ≦ V _MC
<When the V _1, when activating the power booster circuit 29, a short time the neon lamp 30 is lighted. This time
The voltage varies depending on the voltage hysteresis for turning on and off the pass capacitor 13, the resistor 6, and the neon lamp. However, the time is approximately several milliseconds, which appears as a short pulse signal in CHUP.

Next, when V ₂ > V _MC , when the power supply boosting circuit 29 is started up, the neon lamp 30 receives V _MC but V ₂ > V _{MC.
Since it is MC} , the neon lamp 30 does not light. V ₁
When the ≦ V _MC, the neon lamp 30 is lit, thereafter voltage divided by the resistors 5 and 6 will remain lit so applied to the neon lamp.

Accordingly, when the CPU does not output the pulse of the CHUP signal, the main capacitor voltage becomes equal to the light emission permission voltage V.
Less than _2, when exiting a short pulse, the charge stop voltage V less than ₁ in the light-emission enable voltage V ₂ or more, when the left CHUP signal comes much, it is determined that the charge stop voltage V ₁ or more.

FIG. 3B shows this state. t ₁ is a neon lighting delay time, and t ₂ is a lighting time. In other words, if the neon lamp remains lit, the CPU determines that charging has been completed and stops charging, and if the lamp is lit for a short time, permits light emission, that is, permits release, and presses the release button. Accept. When the lamp is not turned on, light emission is disabled, that is, release is not accepted because release is not permitted.

The three states of the charging voltage can be determined by one line transmitting the CHUP signal. That is, based on the signal from this one line, the C
The PU can perform various controls such as continuing charging, stopping charging, releasing permission, releasing non-permission, and displaying them in the viewfinder.

Further, what happens when the release button is pressed during charging of the strobe will be described.
Voltage V _C during charging is equal to the voltage across the resistor 5 to the path capacitor 13 of the electronic flash is Cha - is di. Therefore,
If it is going to check the charging voltage, minutes of the voltage V _C, the voltage across the neon lamp 30 is lowered. Thus, during charging of the electronic flash Lelie - when's is pressed, as shown in FIG. 4, for a period of time t _3, once it stops the charging. Then, the charge of the pass capacitor 13 is discharged through the resistor 5. And the above voltage V _C
Is set to zero volts, and if the voltage check is performed, the voltages at the points B and A become equal, and the neon lamp 30
Voltage does not decrease. FIG. 4 shows this state.

The above is the description of the operation of the first embodiment. The capacitor 31 inserted at the point B for absorbing the ripple causes the diode 24 to have a long reverse recovery time, so-called slow recovery. This can be made unnecessary by using a negative diode.

As described above, according to the above embodiment, a two-level voltage can be detected by the voltage detecting element composed of one neon lamp. Therefore, when the release is pressed, a voltage lower than the charging stop voltage is detected. Sometimes you can give permission to emit light,
The effect of not missing a photo opportunity and rapid continuous shooting can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. The configuration of the flash light emitting circuit of the second embodiment is obtained by adding a diode 37 to the configuration of the light emitting circuit of the first embodiment. That is, as shown in FIG. 5, a diode 37 for blocking a current flowing from the pass capacitor 13 to the resistor 6 is connected to a connection point between the resistors 5 and 6 and the pass capacitor 1.
It is inserted between the connection points of the resistors 3 and 4.

(3) Charging Stop Operation The charging stop operation of the second embodiment is performed by the CH from the CPU.
RG signal with DC / DC converter - data, i.e. start power booster circuit 29, the charging to the main capacitor 16 starts, substantially the same voltage as the voltage V _MC of the main capacitor 16 is generated at point B. At this time, the voltage V _C across the pass capacitor 13 is zero volt. This is because the current flowing from the pass capacitor 13 to the resistor 6 is
This is because they have been blocked by C37.

Therefore, the same main capacitor voltage V _{MC as} that at the point B is applied to the point A. And FIG.
As shown in (A), charging is continued and the neon lighting voltage V ₂
= When the main capacitor voltage V _MC is reached, the neon lamp 3
0 lights up. Then, bypass capacitor 13 neon lighting current is Cha - is di, the voltage at point A is V _MC -V _C. Therefore, when this voltage falls below the neon light-off voltage,
The neon tube 30 goes out. When this is turned off, the voltage corresponding to the hysteresis of the neon tube remains in the pass capacitor 13, but thereafter, when the main capacitor voltage V _MC rises and the voltage at the point A reaches the neon lighting voltage, the neon tube turns on. The capacitor 13 is charged and turned off. While repeating this, the main capacitor voltage V _MC rises. When the connection point C of the resistors 5 and 6 reaches the neon lighting voltage, the neon tube lights up, and thereafter, the neon lighting current flows from the resistor 5 side. Because it is supplied, the neon tube 30 remains lit. Therefore, charging is stopped at this time.

(4) Light Emission Permitting Voltage Detection Operation The operation of the light emission permission voltage detection is the same as that of the first embodiment, and the description thereof will be omitted. However, since the waveforms of the respective parts are slightly different, this is shown in FIG. The difference from the first embodiment is that the voltage at point A does not drop until the neon lamp is turned on during the voltage check. In the first embodiment, the point A is set at the same time when the CHRG signal is turned on.
, The voltage dropped during the lighting delay time t ₁ of the neon tube becomes an error in the detected voltage. To reduce this, it is necessary to increase the constant of the pass capacitor 13. In the second embodiment, the point A is maintained even during the neon lighting delay.
Since the voltage does not fall, a relatively small capacitor is sufficient.

Next, the voltage check during the strobe charge is performed in the same manner as in the first embodiment. However, since the constant of the capacitor 13 is small, the off time t ₃ of the CHRG signal can be short. The determination by the CPU is the same as in the first embodiment.

According to the second embodiment, the detection voltage becomes more accurate, the capacity of the pass capacitor 13 can be reduced, and the cost and the space can be reduced.

[0033]

As described above, according to the present invention, since different voltages can be detected with a simple circuit configuration using one voltage detecting element, a continuous shooting time can be shortened without missing a photo opportunity. Remarkable effect is obtained.
In addition, compared to a voltage detection circuit using a split resistor, an effect of reducing space and cost can be exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram of a flash light emitting device showing the concept of the present invention.

FIG. 2 is an electric circuit diagram of a flash light emitting device according to the first embodiment of the present invention.

FIG. 3 is a timing chart for explaining the operation of the flash light emitting device of the first embodiment.

FIG. 4 is a timing chart for explaining an operation when a release is pressed during charging in the flash light emitting device of the first embodiment.

FIG. 5 is an electric circuit diagram of a flash light emitting device according to a second embodiment of the present invention.

FIG. 6 is a timing chart for explaining the operation of the flash light emitting device of the second embodiment.

FIG. 7 is a diagram showing a curve for charging a main capacitor due to a difference in output voltage of a step-up transformer.

FIG. 8 is an electric circuit diagram showing an example of a conventional flash light emitting circuit.

FIG. 9 is an electric circuit diagram showing another example of a conventional flash light emitting circuit.

FIG. 10 is an electric circuit diagram showing still another example of the conventional flash light emitting circuit.

[Explanation of symbols]

 5, 6 ... voltage dividing resistor (voltage dividing circuit) 13 ... pass capacitor 16 ... main capacitor 27 ... discharge tube 29 ... power supply boosting circuit 30 ... neon lamp (voltage detecting element) 32 ... charging voltage detection Circuit 33: Charge control circuit (CPU) 35: Trigger circuit 37: Diode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-242241 (JP, A) JP-A-4-62797 (JP, A) JP-A-2-193131 (JP, A) 109324 (JP, U) Japanese Utility Model Showa 56-45826 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/32 G03B 15/05

Claims (4)

(57) [Claims] 1. A power supply booster circuit for receiving a booster control signal and boosting a power supply voltage, a main capacitor charged by the boosted voltage of the power supply booster circuit, connected in parallel with the main capacitor, and connected to a pass capacitor and a voltage detector. A voltage dividing circuit for applying a divided voltage of the charging voltage of the main capacitor to a connection point between the pass capacitor and the voltage detecting element, and a boosting operation according to the boosting control signal. A flash light emitting device for detecting a charging voltage of the main capacitor according to an output signal of the voltage detecting element at the time. 2. The flash light emitting device according to claim 1, wherein a diode is connected between a connection point between the pass capacitor and the voltage detecting element and the voltage dividing circuit. 3. A power supply voltage boosting circuit for boosting a power supply voltage in response to a boosting control signal, a main capacitor charged by the boosted voltage by the power supply voltage boosting circuit, and charging for detecting a voltage charged in the main capacitor.
Voltage detecting means, and a main capacitor detected by the charging voltage detecting means.
Sensor voltage is lower than the main capacitor charge completion voltage
Output a repetitive pulse signal if
The voltage of the main capacitor detected by the detection means
And a signal output means for outputting a non-pulse signal when the voltage is equal to or higher than the charge completion voltage of the main capacitor . 4. A power supply voltage is boosted in response to a boost start signal.
Power supply booster circuit and the boosted voltage of this power supply booster circuit.
A main capacitor to be charged , a voltage dividing means for dividing the voltage of the capacitor, and a voltage dividing ratio of the voltage dividing means in response to the boosting start signal.
Changing means for further, flash light emission device being characterized in that comprises a.